Land use change Flashcards
How have krill responded to warming oceans
Moved about 400km further south towards pole. This will affect the animals that feed on them.
Draw the land use transitions graph
P.O.P
We are changing the climate by changing the landscape eg urban heat island affect, deforestation increasing albedo etc
Draw how we can trade off growing crops with ecosystem services
pop.
Why is the arctic under increasing threat
Development, road construction, pipelines etc
For example the road from Inuvik to Tuktoyaktuk in Canada. Build with ice crystal and gravel in winter. Then waiting and in summer it settled then melts. They put loads of insulation in the bottom so warm the road absorbs doesn’t effect surrounding landscape. Costs loads. Altered hydrology of the system. Destroyed research sites. Road is a barrier
In long run cumulative effect of such activities will cause biodiversity losses and reduce arctic wilderness heritage considerably. eg road block the movement of small animals, expose large animals to heavy hunting pressure, and poaching and cause sedimentation in ricers from erosion.
Cumulative impacts more serious in the arctic too bc the permafrost magnifies disturbances and makes restoration efforts difficult or impossible
Wilderness areas in Norway
Wilderness: areas lying 5km or more from roads, railways, and regulated water courses. During the last century undisturbed or pristine wilderness areas have reduced from 48% of countryside in 1900 to 11.8% in 1998. Trend largely because of agriculture, forestry, and hydro electric development
Huge fragmentation of landscape. oil funds everything in Norway.
Urban ecology
Integrates natural and social sciences to study these radically altered local environments and their regional and global effects.
Ecologists shunned urban areas for most of the 1900s with the result that the ecological knowledge contributed little to solving urban environmental problems.
Pic of graph of people living in urban env
Global change and urban ecosystems
Grimm et al
Focussed on 5 major tees of global environmental change that affect and are affected by urban ecosystem
- change in land use cover
- biogeochemical cycles
- climate
- hydrosystems
- and biodiversity
Unprecedented rates of urban population growth over past century ave occurred n <3% on the global terrestrial surface and yt, the impact has been global
78% of C emissions,
60% of residential water use
76% of wood used for industrial purposes
attributed to cities
Land change to build cities and support the demand of urban population that drives other types of environmental change
Issues of habitat fragmentation studies
- difficult to interpret
- measurement of patch rather than at landscape scale
- most measure fragmentation in ways that do not distinguish between habitat loss and fragmentation itself
Manipulating a landscape to try and fragment it is difficult. Habitat loss doesn’t necessarily mean fragmentation.
- since habitat fragmentation is a landscape process, sample size is typically only two (one continuous, one fragmented)- so inferences about the effect of fragmentation are weak
- characterisation of habitat fragmentation is strongly qualitative - each landscape can only be in 2 state = fragmented or continuous
Four effects of fragmentation
(a) Reduction in habitat amount
(b) Increase in number of habitat patches
(c) Decrease in sizes of habitat patches
(d) Increase in isolation of patches
((e) creates edges )
Rarely are all four effects considered together. Does it matter what measure of fragmentation a researcher uses? it depends, cannot talk about fragmentation without all 4. When you do one you often do others.
Define habitat fragmentation
When a large expanse of a particular, broadly defined habitat ‘type’ is reduced to smaller patches that are isolated by surround, but different, habitats
Surrounding habitat is typically defined at matrix, and in the case of forest fragmentation typically means ‘degraded’ habitat
Implications of the effects of fragmentation
- Smaller an area often fewer spp it contained
- The more isolated a population, less chance immigrants will rescue it from catastrophes etc
- Edges allow the invasion of alien spp, make the microclimate intolerable, incr access to humans and lead to cascading ecological effects (eg fire penetration). Can go deep into forests about 100m
Destruction and degradation
The primary cause of declines in global biodiversity
Destruction typically leads to fragmentation. Long term changes in structure and function of the remaining habitats.
Biogeography of oceanic islands provided early theoretical framework to understand effect of fragmentation. ‘islands and sea’
Central to controversy has been the lingering uncertainty about the role of decr fragment size and incr isolation relative to the widespread and pervasive effects of habitat loss in explaining declines of biodiversity and degradation of ecosystem.
fragmentation has multiple, simultaneous, interwoven effects that can operate over potentially longterm scales. Rigorous designs and long term implementation of studies can overcome limitations of observational studies. One spans 35 years on 5 continents
The worlds Forests and fragmentation
Satellite data can reveal info about human activity and ho it is affecting he landscape. Lost >1/3rd of forest cover worldwide –> likely to suffer from fragmentation
Analysis revealed nearly 20% of the worlds remaining forest is within 100m of an edge
More than 70% are within 1km of forest edge. Most forests are well within the range where human activities alter microclimate, and non-forest spp may influence and degrade forest ecosystems.
Largest contiguous expanses of forests are in the humid tropical regions of the amazon and congo river basins. Large areas of more disjunct forest in SE Asia, New Guinea, and the boreal biomes
Brazil amazon vs brazil atlantic rainforests
Brazil amazon
- rapidly changing frontier, yet most forests remain contiguous and far from edge despite recent increases in fragmentation
- forest proportion further than 1km from the forest edge decreased from 95% to 75%
brazil atlantic
- largely deforested landscape, cleared for agriculture and logged for timber over the past 3 centuries. Remaining forest dominated by small fragments, most small than 100ha and within 1000m of forest edge
- within 1km from edge forest decr from 90% (historically) to <9% today
Ha = 100x100m
Why are long term experiments better
dont have issues that come with observational eg
- lack of rigorous controls
- replication
- randomisation
- or baseline data
Observational have limited ability to isolate the effect of fragmentation from concomitant habitat loss and degradation
Remnant fragments are embedded in different types and quality of surrounding habitats also influences biodiversity and ecosystem production
eg time dynamics- slash and burn agriculture- how long they are there will impact how degraded the habitat is, eg if ALL nutrients removed= worse
Long term fragmentation experiments
Image on essay cues
They manipulate species components and control for confounding effects
Long term experiments can detect lagged and chronic impacts
Summary of their findings:
- reduced area, increased isolation and increased proportion of edge habitat reduced seed predation and herbivory
- incr proportion of edge increased fledging predation that had the effect of reducing bird fecundity
- reduced fragment area and increased isolation reduced abundance of birds, mammals, insects, and plants. perhaps bc of reduced movement and abundance, and ability of spp to persist lower. Often entire communities changes
Tropical forests
- reduced fragment size and increased proportion of edge habitat caused shifts in the physical environment that led to the loss of large, old trees in favour of pioneer trees with subsequent impact on community composition and insects
Grasslands
- fragment size also affected succession rate, such that increase light penetration altered seed pools in smaller fragments and impeded the rate of ecological succession relative to larger fragments
All aspects of fragmentation degraded function including reduced C and N retention, productivity, and pollination
Delayed effects of fragmentation on ecosystem degradation
(A) The extinction debt represents a delayed loss of species due to fragmentation.
(B) The immigration lag represents differences in species richness caused by smaller fragment area or increased isolation during fragment succession.
(C) The ecosystem function debt represents delayed changes in ecosystem function due to reduced fragment size or increased isolation.
As predicted by theory (36), the extinction debt appears to
take longer to pay in larger fragments.
After more than a decade, immigration lags resulted in 5% fewer species after 1 year, and 15% fewer species after 10 years in small or isolated fragments compared to large or connected fragments (Fig. 4B).
An ecosystem function debt is manifest both as delayed changes in nutrient cycling and as changes to plant and consumer biomass. Loss of function amounted to 30% after 1 year, rising to 80% after a decade in small and isolated fragments when compared to larger and more connected fragments (Fig. 4C). Functional debts can result from biodiversity loss, as when loss of nutrients and reduction in decomposition are caused by simplification of food webs. Alternatively, the impact is exhibited through pathways whereby fragmentation changes biotic (for example, tree density in successional
systems) or abiotic conditions (for example, light regimes or humidity) in ways that alter and potentially impair ecosystem function eg carbon soil dynamics
How much does fragmentation reduce biodiversity by
An experiment spanning multiple biomes, scales, 35 years, and 5 continents demonstrates that fragmentation reduces biodiversity by 13-75% and impairs key ecosystem functions by decr biomass and altering nutrient cycles
Effects greatest in smallest and most isolated habitats, and they magnify over time
Need to improve landscape connectivity! bc reduce extinction rates and help maintain ecosystem services
